doc/man7/provider-digest.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 provider-digest - The digest library E<lt>-E<gt> provider functions
   6
   7 =head1 SYNOPSIS
   8
   9 =for openssl multiple includes
  10
  11  #include <openssl/core_dispatch.h>
  12  #include <openssl/core_names.h>
  13
  14  /*
  15   * Digests support the following function signatures in OSSL_DISPATCH arrays.
  16   * (The function signatures are not actual functions).
  17   */
  18
  19  /* Context management */
  20  void *OSSL_FUNC_digest_newctx(void *provctx);
  21  void OSSL_FUNC_digest_freectx(void *dctx);
  22  void *OSSL_FUNC_digest_dupctx(void *dctx);
  23
  24  /* Digest generation */
  25  int OSSL_FUNC_digest_init(void *dctx, const OSSL_PARAM params[]);
  26  int OSSL_FUNC_digest_update(void *dctx, const unsigned char *in, size_t inl);
  27  int OSSL_FUNC_digest_final(void *dctx, unsigned char *out, size_t *outl,
  28                             size_t outsz);
  29  int OSSL_FUNC_digest_digest(void *provctx, const unsigned char *in, size_t inl,
  30                              unsigned char *out, size_t *outl, size_t outsz);
  31
  32  /* Digest parameter descriptors */
  33  const OSSL_PARAM *OSSL_FUNC_digest_gettable_params(void *provctx);
  34
  35  /* Digest operation parameter descriptors */
  36  const OSSL_PARAM *OSSL_FUNC_digest_gettable_ctx_params(void *dctx,
  37                                                         void *provctx);
  38  const OSSL_PARAM *OSSL_FUNC_digest_settable_ctx_params(void *dctx,
  39                                                         void *provctx);
  40
  41  /* Digest parameters */
  42  int OSSL_FUNC_digest_get_params(OSSL_PARAM params[]);
  43
  44  /* Digest operation parameters */
  45  int OSSL_FUNC_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
  46  int OSSL_FUNC_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
  47
  48 =head1 DESCRIPTION
  49
  50 This documentation is primarily aimed at provider authors. See L<provider(7)>
  51 for further information.
  52
  53 The DIGEST operation enables providers to implement digest algorithms and make
  54 them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
  55 L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
  56
  57 All "functions" mentioned here are passed as function pointers between
  58 F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
  59 B<OSSL_ALGORITHM> arrays that are returned by the provider's
  60 provider_query_operation() function
  61 (see L<provider-base(7)/Provider Functions>).
  62
  63 All these "functions" have a corresponding function type definition
  64 named B<OSSL_{name}_fn>, and a helper function to retrieve the
  65 function pointer from an B<OSSL_DISPATCH> element named
  66 B<OSSL_FUNC_{name}>.
  67 For example, the "function" OSSL_FUNC_digest_newctx() has these:
  68
  69  typedef void *(OSSL_OSSL_FUNC_digest_newctx_fn)(void *provctx);
  70  static ossl_inline OSSL_OSSL_FUNC_digest_newctx_fn
  71      OSSL_FUNC_digest_newctx(const OSSL_DISPATCH *opf);
  72
  73 B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
  74 macros in L<openssl-core_dispatch.h(7)>, as follows:
  75
  76  OSSL_FUNC_digest_newctx               OSSL_FUNC_DIGEST_NEWCTX
  77  OSSL_FUNC_digest_freectx              OSSL_FUNC_DIGEST_FREECTX
  78  OSSL_FUNC_digest_dupctx               OSSL_FUNC_DIGEST_DUPCTX
  79
  80  OSSL_FUNC_digest_init                 OSSL_FUNC_DIGEST_INIT
  81  OSSL_FUNC_digest_update               OSSL_FUNC_DIGEST_UPDATE
  82  OSSL_FUNC_digest_final                OSSL_FUNC_DIGEST_FINAL
  83  OSSL_FUNC_digest_digest               OSSL_FUNC_DIGEST_DIGEST
  84
  85  OSSL_FUNC_digest_get_params           OSSL_FUNC_DIGEST_GET_PARAMS
  86  OSSL_FUNC_digest_get_ctx_params       OSSL_FUNC_DIGEST_GET_CTX_PARAMS
  87  OSSL_FUNC_digest_set_ctx_params       OSSL_FUNC_DIGEST_SET_CTX_PARAMS
  88
  89  OSSL_FUNC_digest_gettable_params      OSSL_FUNC_DIGEST_GETTABLE_PARAMS
  90  OSSL_FUNC_digest_gettable_ctx_params  OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
  91  OSSL_FUNC_digest_settable_ctx_params  OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
  92
  93 A digest algorithm implementation may not implement all of these functions.
  94 In order to be usable all or none of OSSL_FUNC_digest_newctx, OSSL_FUNC_digest_freectx,
  95 OSSL_FUNC_digest_init, OSSL_FUNC_digest_update and OSSL_FUNC_digest_final should be implemented.
  96 All other functions are optional.
  97
  98 =head2 Context Management Functions
  99
 100 OSSL_FUNC_digest_newctx() should create and return a pointer to a provider side
 101 structure for holding context information during a digest operation.
 102 A pointer to this context will be passed back in a number of the other digest
 103 operation function calls.
 104 The parameter I<provctx> is the provider context generated during provider
 105 initialisation (see L<provider(7)>).
 106
 107 OSSL_FUNC_digest_freectx() is passed a pointer to the provider side digest context in
 108 the I<dctx> parameter.
 109 This function should free any resources associated with that context.
 110
 111 OSSL_FUNC_digest_dupctx() should duplicate the provider side digest context in the
 112 I<dctx> parameter and return the duplicate copy.
 113
 114 =head2 Digest Generation Functions
 115
 116 OSSL_FUNC_digest_init() initialises a digest operation given a newly created
 117 provider side digest context in the I<dctx> parameter.
 118 The I<params>, if not NULL, should be set on the context in a manner similar to
 119 using OSSL_FUNC_digest_set_ctx_params().
 120
 121 OSSL_FUNC_digest_update() is called to supply data to be digested as part of a
 122 previously initialised digest operation.
 123 The I<dctx> parameter contains a pointer to a previously initialised provider
 124 side context.
 125 OSSL_FUNC_digest_update() should digest I<inl> bytes of data at the location pointed to
 126 by I<in>.
 127 OSSL_FUNC_digest_update() may be called multiple times for a single digest operation.
 128
 129 OSSL_FUNC_digest_final() generates a digest started through previous OSSL_FUNC_digest_init()
 130 and OSSL_FUNC_digest_update() calls.
 131 The I<dctx> parameter contains a pointer to the provider side context.
 132 The digest should be written to I<*out> and the length of the digest to
 133 I<*outl>.
 134 The digest should not exceed I<outsz> bytes.
 135
 136 OSSL_FUNC_digest_digest() is a "oneshot" digest function.
 137 No provider side digest context is used.
 138 Instead the provider context that was created during provider initialisation is
 139 passed in the I<provctx> parameter (see L<provider(7)>).
 140 I<inl> bytes at I<in> should be digested and the result should be stored at
 141 I<out>. The length of the digest should be stored in I<*outl> which should not
 142 exceed I<outsz> bytes.
 143
 144 =head2 Digest Parameters
 145
 146 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 147 these functions.
 148
 149 OSSL_FUNC_digest_get_params() gets details of the algorithm implementation
 150 and stores them in I<params>.
 151
 152 OSSL_FUNC_digest_set_ctx_params() sets digest operation parameters for the
 153 provider side digest context I<dctx> to I<params>.
 154 Any parameter settings are additional to any that were previously set.
 155
 156 OSSL_FUNC_digest_get_ctx_params() gets digest operation details details from
 157 the given provider side digest context I<dctx> and stores them in I<params>.
 158
 159 OSSL_FUNC_digest_gettable_params() returns a constant B<OSSL_PARAM> array
 160 containing descriptors of the parameters that OSSL_FUNC_digest_get_params()
 161 can handle.
 162
 163 OSSL_FUNC_digest_gettable_ctx_params() and
 164 OSSL_FUNC_digest_settable_ctx_params() both return constant
 165 B<OSSL_PARAM> arrays as descriptors of the parameters that
 166 OSSL_FUNC_digest_get_ctx_params() and OSSL_FUNC_digest_set_ctx_params()
 167 can handle, respectively.  The array is based on the current state of
 168 the provider side context if I<dctx> is not NULL and on the provider
 169 side algorithm I<provctx> otherwise.
 170
 171 Parameters currently recognised by built-in digests with this function
 172 are as follows. Not all parameters are relevant to, or are understood
 173 by all digests:
 174
 175 =over 4
 176
 177 =item "blocksize" (B<OSSL_DIGEST_PARAM_BLOCK_SIZE>) <unsigned integer>
 178
 179 The digest block size.
 180 The length of the "blocksize" parameter should not exceed that of a B<size_t>.
 181
 182 =item "size" (B<OSSL_DIGEST_PARAM_SIZE>) <unsigned integer>
 183
 184 The digest output size.
 185 The length of the "size" parameter should not exceed that of a B<size_t>.
 186
 187 =item "flags" (B<OSSL_DIGEST_PARAM_FLAGS>) <unsigned integer>
 188
 189 Diverse flags that describe exceptional behaviour for the digest:
 190
 191 =over 4
 192
 193 =item B<EVP_MD_FLAG_ONESHOT>
 194
 195 This digest method can only handle one block of input.
 196
 197 =item B<EVP_MD_FLAG_XOF>
 198
 199 This digest method is an extensible-output function (XOF) and supports
 200 setting the B<OSSL_DIGEST_PARAM_XOFLEN> parameter.
 201
 202 =item B<EVP_MD_FLAG_DIGALGID_NULL>
 203
 204 When setting up a DigestAlgorithmIdentifier, this flag will have the
 205 parameter set to NULL by default.  Use this for PKCS#1.  I<Note: if
 206 combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
 207
 208 =item B<EVP_MD_FLAG_DIGALGID_ABSENT>
 209
 210 When setting up a DigestAlgorithmIdentifier, this flag will have the
 211 parameter be left absent by default.  I<Note: if combined with
 212 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 213
 214 =item B<EVP_MD_FLAG_DIGALGID_CUSTOM>
 215
 216 Custom DigestAlgorithmIdentifier handling via ctrl, with
 217 B<EVP_MD_FLAG_DIGALGID_ABSENT> as default.  I<Note: if combined with
 218 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 219 Currently unused.
 220
 221 =back
 222
 223 The length of the "flags" parameter should equal that of an
 224 B<unsigned long int>.
 225
 226 =back
 227
 228 =head2 Digest Context Parameters
 229
 230 OSSL_FUNC_digest_set_ctx_params() sets digest parameters associated with the
 231 given provider side digest context I<dctx> to I<params>.
 232 Any parameter settings are additional to any that were previously set.
 233 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 234
 235 OSSL_FUNC_digest_get_ctx_params() gets details of currently set parameters
 236 values associated with the give provider side digest context I<dctx>
 237 and stores them in I<params>.
 238 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 239
 240 =head1 RETURN VALUES
 241
 242 OSSL_FUNC_digest_newctx() and OSSL_FUNC_digest_dupctx() should return the newly created
 243 provider side digest context, or NULL on failure.
 244
 245 OSSL_FUNC_digest_init(), OSSL_FUNC_digest_update(), OSSL_FUNC_digest_final(), OSSL_FUNC_digest_digest(),
 246 OSSL_FUNC_digest_set_params() and OSSL_FUNC_digest_get_params() should return 1 for success or
 247 0 on error.
 248
 249 OSSL_FUNC_digest_size() should return the digest size.
 250
 251 OSSL_FUNC_digest_block_size() should return the block size of the underlying digest
 252 algorithm.
 253
 254 =head1 BUGS
 255
 256 The EVP_Digest() and EVP_DigestFinal_ex() libcrypto API calls do not
 257 expect the digest size to be larger than EVP_MAX_MD_SIZE. Any algorithm which
 258 produces larger digests is unusable with those API calls.
 259
 260 =head1 SEE ALSO
 261
 262 L<provider(7)>, L<OSSL_PROVIDER-FIPS(7)>, L<OSSL_PROVIDER-default(7)>,
 263 L<OSSL_PROVIDER-legacy(7)>
 264
 265 =head1 HISTORY
 266
 267 The provider DIGEST interface was introduced in OpenSSL 3.0.
 268
 269 =head1 COPYRIGHT
 270
 271 Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
 272
 273 Licensed under the Apache License 2.0 (the "License").  You may not use
 274 this file except in compliance with the License.  You can obtain a copy
 275 in the file LICENSE in the source distribution or at
 276 L<https://www.openssl.org/source/license.html>.
 277
 278 =cut